Automatic boiler blowdown apparatus and method

ABSTRACT

An apparatus and method for automatically blowing down a boiler. In operation, the boiler is blown down by discharging sedimentcontaining water into an intermediate or holding tank rather than directly to a drain. In one form of the apparatus, at a predetermined time, the holding tank is pressurized through actuation of a valve in a line leading from the boiler head space to the holding tank, and after this valve is subsequently closed and the steam is permitted to condense in the holding tank, the blowdown valve is caused to open and a measured quantity of sediment-containing water is discharged into the holding tank. In keeping with the invention, after the sediment-containing water in the holding tank cools to a predetermined temperature, the holding tank is again opened to pressure from the boiler head space which forces the water and sediment to drain from the tank. When the holding tank discharge temperature rises in response to the presence of the expanded steam pressurizing the holding tank, the tank drain valve closes to prevent escape of expanded steam or vapor. Subsequent closing of the steam inlet valve leaves the holding tank pressurized and the apparatus thereby automatically reset for the operation to repeat. The other embodiments of the apparatus include controls responsive to predetermined time intervals only in the normal operation and pressure and/or temperature sensing controls and/or electrodes are used as auxiliary or safety devices.

United States Patent 1191 Andersen 14 1 Sept. 30, 1975 [54] AUTOMATIC BOILER BLOWDOWN APPARATUS AND METHOD Charles M. Andersen, 5318 W. 95th St.. Oak Lawn, 111. 60453 1221 Filed: Nov. 1, 1974 211 App]. NO.2519,911

[761 Inventor:

Primary E.\'t1minerKenneth W. Sprague [57] ABSTRACT An apparatus and method for automatically blowing down a boiler. In operation. the boiler is blown down by discharging sediment-containing water into an intermediate or holding tank rather than directly to a drain. In one form of the apparatus. at a predetermined time. the holding tank is pressurized through actuation of a valve in a line leading from the boiler head space to the holding tank, and after this valve is subsequently closed and the steam is permitted to condense in the holding tank, the blowdown valve is caused to open and a measured quantity of sedimentcontaining water is discharged into the holding tank. In keeping with the invention, after the sedimentcontaining water in the holding tank cools to a predetermined temperature, the holding tank is again opened to pressure from the boiler head space which forces the water and sediment to drain from the tank. When the holding tank discharge temperature rises in response to the presence of the expanded steam pressurizing the holding tank, the tank drain valve closes to prevent escape of expanded steam or vapor. Subsequent closing of the steam inlet valve leaves the holding tank pressurized and the apparatus thereby automatically reset for the operation to repeat. The other embodiments of the apparatus include controls responsive to predetermined time intervals only in the normal operation and pressure and/or temperature sensing controls and/or electrodes are used as auxiliary or safety devices.

13 Claims, 6 Drawing; Figures US. Patent Sept. 30,1975

PRESSURIZE HOLDING TANK ISOLATE HOLDING TANK 8 CONDENSE STEAM BLOW BOILER DOWN INTO EVACUATED TANK EXPEL SEDIMENT 8 WATER FROM HOLDING TANK REPRESSURIZE HOLDING TANK (RESET) wl l l i i l l AUTOMATIC BOILER BLOWDOWN APPARATUS AND METHOD BACKGROUND OF THE INVENTION The present invention relates to a so-called blowdown device for steam boilers and more particularly to a device providing automatic blowdown of a steam boiler at periodic intervals and providing an operating sequence whereby no steam or highly heated water is passed directly in the atmosphere, and where the sequence of operation is automatically initiated and terminated in response both to a time interval and, in some cases, to conditions within the system.

It is well known that there are still in existence a large number of boilers, such as the Scotch Marine type boiler, which are large enough to require frequent blowdown, but which are not so large as to require continuous attendance by an operating engineer. There are likewise a large number of boilers in existence, which for one reason or another, require fairly frequent blowdown, even in spite of the fact that means are provided to minimize scaling, accumulation of deposits and other conditions requiring alleviation by periodic blowdown of the boiler. I

In the stationary engineering field, it is more or less conceded that periodic blowdown is often not properly attended to, and this usually occurs either because the operator feels blowdown is not necessary or merely from neglect. It is known, however, that failure to blow the boiler down at the necessary intervals results in an undesirable accumulation of sediment and other deposits inside the boiler, and this in turn results in scaling and encrusting of the pipes, valve, and controls associated with the boiler. A boiler which is not blown down with proper frequency is one which, among other things, transfers heat poorly and is consequently inefficient in use. Moreover, such a boiler does not perform to specifications and may be required to be taken out of service for cleaningat inconvenient times or at undesirably frequent intervals. Still further, such boilers often become so damaged as to require early replacement. 7

In certain cases, automatic blowdown devices have been constructed, but many of these are unduly expensive and complex, or are unreliable, or call for operations which create the risk of live steam being released to the atmosphere, or which otherwise do not comply with various codes and which are, therefore, not approved by building authorities. Other prior art devices are not readily adaptable to existing boilers.

In view of the need for an apparatus of the type referred to above, and in view of the failure of the prior art to provide such device, it is an object of the present invention to provide an improved automatic blowdown device for a boiler.

It is another object of the invention to provide a blowdown device which minimizes or eliminates the possibility that live steam or steam under high pressure may be discharged to the atmosphere during boiler blowdown. By atmosphere, as used herein, is meant any place at atmospheric pressure exterior to the boiler, whether a drain pipe, a sewer, an open tankor collector, or otherwise.

A further object of the invention blowdown system wherein means is provided for receiving sediment-containing water, blown down from the boiler and for holding the sediment and water until is to provide a boiler the water has cooled sufficiently to permit safe discharge -thereof, and which will not be so hot as to tend to crack sewer tile or pipe.

Another object is to provide an apparatus with an evacuable reservoir for boiler sediment and water, which may also be pressurized to accelerate discharge of the contents thereof.

Another object is to provide a boiler blowdown system containing a valve arrangement adapted for positive prevention of undesirable direct communication between the boiler blowdown line and the receptacle or drain for the discharge.

A still further object is to provide a boiler blowdow apparatus with a boiling tank for receiving boiler sediment in water, with the tank further including heat exchange means to accelerate condensation of steam'or vapor in the holding tank.

Another objectis to provide a method and apparatus for blowing down a boiler whereby the holding tank for the sediment-containing water may be evacuated so as to insure rapid filling thereof, to prevent transmission of shock to the lines and as an aid in providing positive control action and proper safeguards.

A still further object is to provide a method and apparatus of boiler blowdown which isadapted to fully automatic operation, that is, a method and apparatus wherein the blowdown cycle is initiated, carried out, and then terminated by a step which resets the controls for repeating the operation.

Yet another object is to provide an automatic boiler blowdown apparatus. and method which includes means for receiving a charge of sediment-containing water from a boiler to be blown down, means for holding a charge until it is cooled sufficiently to avoid presentation of a safety hazard, and means for draining the sediment and water from the tank, all of such functions being carried out according to a predetermined sequence.

Another object is to provide a method of boiler oper- ,ation wherein the sediment-containing water is transferred during blowdown from the boiler to a boiling tank rather than to the atmosphere, wherein the tank is prepared for receiving the charge of sedimentcontaining water prior to reception thereof, and wherein sediment-containing blowdown water is discharged from the holding tank, preferably under positive pressure, only after the water has cooled and any steam or vapor present therewith has condensed, so that the hazard of venting the boiler directly to atmosphere during blowdown is avoided.

Another object is to provide an apparatus wherein the water containing the sediment will flow rapidly and turbulently into the holding tank, and wherein air locks in the blowdown line may be avoided.

A still further object is to provide a boiler blowdown system which includes a holding tank, means providing communication between the tank and the boiler headspace, means providing communication between the boiler blowdown drain and the holding tank, means for detecting the pressure in the holding tank, means for controlling' flow bf steam between the tank and the headspace for a'predetermined time at selected intervals, means for controlling water flow between the blowdown outlet and the holding tank in response to conditions in the holding tank, and means for draining the tank subsequent to filling thereof, with the tank, the blowdown line and the drain being constructed and arranged so that the tank drain is closed when the blowdown line is open, and so that the blowdown line is closed when the tank drain is open.

The exact manner in which the above objects and advantages, including objects and advantages inherentin the invention, are carried into practice, will become more clearly apparent when reference is made to the following detailed description of the preferred embodiments of the invention set forth by way of example, and shown in the accompanying drawings, wherein like reference numbers indicate corresponding parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially schematic view of one form of apparatus of the invention, showing certain portions thereof in section;

FIG. 2 is a diagrammatic view showing the sequence of operations of the method of the invention; and

FIGS. 3a-3d show an operating sequence of the control system of a modified form of apparatus according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION Although it will be understood that the present invention may be embodied in a number of forms, and is suitable for use with different forms of boilers, and various operating pressures, one embodiment will be described wherein a boiler of the so-called Scotch Marine type is used in a stationary installation and is adapted to operate under steam pressure of to pounds per square inch, gauge (p.s.i.g.), for example.

Referring now to the drawings in greater detail,

FIG. 1 shows a boiler generally designated 10 and a blowdown apparatus and control mechanism generally designated 12 connected to and associated with the boiler 10. The boiler 10 includes an exterior, generally cylindrical sidewall portion 14 adapted to receive water in the interior 16 thereof and having a pair of draft tubes 18 extending longitudinally through the interior 16 in a customary manner. The water in the boiler is maintained at a level such that the draft tubes 18 are covered by the water and so that a head space 22 is maintained above the water level. For this purpose, water periodically enters the boiler through line 20, from a makeup tank (not shown) in a manner well known in the art.

Extending upwardly from the top of the boiler 10 is principal steam outlet pressure line 24, and extending downwardly from the bottom of the boiler is the vertically extending portion 26 of the blowdown line 28.A drain valve 30 is fitted to the bottom of the line 26. Extending from the main steampressure line 24 is a holding tank pressurizing line 32 attached at one end thereof with a holding tank generally designated 34. A

pressurizing line valve 36 is adapted to be actuated by a solenoid 38 or the like electrically connected as at 40 to a sequence timer 42.

The holding tank 34 is shown to include an upper wall portion 44, a lower wall portion 46, and sidewall portions 48, as well as an exterior water jacket 50 having inlet and outlet openings 52, 54, respectively. Water jacketing or providing heat exchange capability for the holding tank 34 is an optional feature of the invention which will be referred to elsewhere herein.

As shown in FIG. 1, the holding tank 34 has associated therewith control means in the form of a pressure sensor 56 and an electrical connection 58 to a relay 60 or the like. The holding tank 34 includes a tank drain line 62 extending downwardly from the bottom wall 46 of the tank 34.

The blowdown line 28 is shown to include a valve 66 operated by a relay 68 which is electrically connected as at 70 to the holding tank sensor 56 and control relay 60.

An important feature of the invention is the provision of the valve assembly generally designated 70 and lying in the line 28 between the boiler 10 and the holding tank 34. The valve assembly 70 preferably is a threeconnection valve having two operative positions and one or more closed positions. As shown schematically in FIG. 1, valve assembly 70 has a spool 71 constructed and arranged in such a way that the communication is established between only two of the openings in the valve housing 73 at any one time. In this way, the valve can permit communication between the boiler 10 and the tank 34 through the blowdown line 28; or between the tank drain line 62 and the drain connector 64. Preferably the spool 71 of the valve assembly 70 is motorized for accurate control of the movement thereof. FIG. 1 also shows that a temperature sensing valve assembly 67 is attached to the end of line 64, and that a drain line 69 extends downwardly therefrom. The valve assembly 66 may consist of one or more individual valves, and operation thereof is referred to in greater detail elsewhere herein.

Referring now to the operation of the apparatus of the invention, it will be assumed that a necessary amount of water has been charged into the interior 16 of the boiler 10 through line 20 from a makeup tank (not shown), and that steam is being generated in the head space 22 to pressurize the line 24 and to heat those portions of the system connected thereto. At a predetermined time, as established by the automatic or manually set timer 42, the solenoid 38 is actuated by an impulse delivered through conductors 40, causing the normally closed, two-connection, two-position valve 36 to open and to establish communication between the principal steam line 24 and the holding tank 34.

After a predetermined time, also established by the timer 42, the valve 36 is closed, thereby leaving the holding tank 34 filled with steam at a pressure equal to that in the headspace 22 of the boiler 10. Inasmuch as the valve 66 is now closed, even with the spool 71 of the valve 70 arranged as shown, there is no way for steam to escape from the holding tank 34. After a suitable period of time, the steam in the tank 34 condenses, and collects as water in the bottom of the holding tank. The condensate is very small in volume in relation to the volume in the interior of the tank 34, and the level of the water in the tank following condensation thereof might be, for example, the level indicated as L-l in FIG. 1.

As a result of the condensation of steam and vapor, the pressure in the tank 34 is lowered and actually becomes a partial vacuum, typically showing a gauge reading of minus 5 to 10 inches of mercury, or in some cases, an even lower gauge reading.

After the vacuum reaches a predetermined level indicative of complete steam condensation, and indicating that the temperature in the tank 34 has decreased to well below the boiling point of water, the pressurevacuum sensor 56, at a predetermined pressure level (actually a partial vacuum level), sends a signal through the conductor 58 to a relay 60, which in turn actuates the solenoid 68, rapidly opening the twoconnection, two-position, normally closed blowdown valve 66, thereby causing the water and sediment contained in the bottom of the boiler interior 16 to pass rapidly and turbulently through the line 28, through valve assembly 70, and into the interior of the holding tank 34. Because of the partial vacuum in the tank, even partial vaporization of the water passing through the blowdown line will not cause a hammering or shock phenomenon in the lines or in the tank 34. This may be continued until a suitable predetermined pressure is reached, which again causes the detector 56 to signal the relay 60 to de-energize the solenoid 68, permitting the valve 66 to close. When valve 66 is closed, therefore, communication between the interior 16 of the boiler and the holding tank 34 is interrupted.

Typically, the holding tank may not be entirely filled, but a substantial portion of the tank will be occupied, with sediment-containing water, which may typically rise to the level shown at L-2 in the tank 34.

At this point, the tank 34 has received a charge of sediment-containing water, the boiler has been blown down, and the blown-down boiler water in the tank 34 is permitted or induced to cool. FIG. 1 shows that the tank 34 contains a jacket 50, and that cooling water is flowing therein, so as to cool the holding tank rapidly.

If desired, water acting to cool the holding tank 34 may be piped to the makeup tank (not shown); the steam condensing in tank 34 will thus serve a heatexchange function.

When the sediment and water have cooled to a safe temperature, the spool 71 of the valve assembly 70 is rotated by its associated motor 75 so as to place the lines 62, 64 in communication with each other, and to permit the water to be drained from the tank 34, provided that the valve assembly 67 is open to drain line 69. In a preferred operating sequence, draining of the sediment-containing water is accelerated by again opening valve 36 under the control of the timer 42, so that a high positive pressure is placed in the headspace above the water in the tank 34. When the water in the tank 34 has reached the desired lower temperature, it is permitted to pass through lines 62, 64, and is thus directed over the temperature-sensitive valve assembly 67. As long as this water remains cool, the normally open valve assembly 67 remains open so as to permit draining of the water from the tank 34. However, when the steam and vapor forming a pressure head on the water in the tank 34 begin to flow through the valve assembly 67, the valve closes. Thereafter, the spool 71 of the valve assembly 70 rotates under the control of the motor 75 to a position preventing passage of steam through the tank 34.

At this point, the valve 36 remains open for a predetermined length of time sufficient to allow the steam, which has purged the water in tank 34, to fill the tank 34 with steam under a pressure euqal to that in the main steam line 24. Thereupon, the valve 36 again closes, and the blowdown operation is ready to be repeated. as described above. It will be realized that the above description referred to an initial condition wherein there was no charge of water in the tank 34; after this tank is once charged however, it will be drained and refilled in the above-described sequence.

Thus, the apparatus of the invention will initiate opera tion in either a filled or an unfilled condition of the tank 34. It will also be understood that, as the water level in the interior 16 of the boiler 10 is reduced, and the headspace 22 becomes larger, the boiler receives periodic charges of water from the makeup tank (not shown) through the pipe 20 in a manner well known in the art.

FIG. 2 shows a diagrammatic representation of the preferred operating sequence of the apparatus of the invention, which is paraphrased and set forth below. Briefly, however, the sequence is as follows:

First, the holding tank is pressurized from the supply of steam in the boiler. Next, the holding tank is isolated and the pressure therein reduced as the steam condenses. Thereafter, the boiler is blown down into the holding tank. Next, the sediment-containing water is forced from the holding tank under positive pressure. Finally, the holding tank is repressurized, and the apparatus is reset for repetition of the operation. Certain of these steps may be modified oreliminated in practice, as referred to elsewhere herein in greater detail.

Referring now to an alternate construction of the apparatus, FIGS. 3a-3d show an arrangement whereby a valve assembly a similar to its counterpart 70 in FIG. 1, and having a spool 71a, is provided and shown to be operable in response to a signal received from a timer 80 and to be driven by a motor a in such a way that the spool 71a may be moved between the various positions shown in FIGS. 3a3d. In FIG. 3a, the spool is shown to be positioned so as to block all ports, and to be adapted for clockwise rotation under control of the motor 75a.

In the form of apparatus shown in FIGS. 3a-d, the valve 66 in line 28, the relay 68, the conductor 70 and the associated pressure and vacuum sensor and controls 56, 58, 60 are eliminated, and the timer is substituted therefor. The motor 75a powers the valve spool 71a.

In the operation of this form of apparatus, the spool 70a is initially in the position shown in FIG. 3a, that is, all ports are blocked. This insures that the blowdown line 28 is blocked, as well as the tank drain line 62. As the timer 80 indicates that a blowdown operation is indicated, the motor 75a is energized and the spool is moved to the position of FIG. 3, whereupon the blowdown line 28 is opened and water under boiler pressure passes to the evacuated tank 34. After elapse of a desired time, as indicated by the timer 80, the valve spool 71a is advanced to the position of FIG. 3c, which closes blowdown line 28 and leaves the tank 34 under a relatively high pressure, filled with hot water and/or steam and vapor.

In this connection, it will be understood that a certain amount of steam and vapor may form as the superheated water passes from the boiler, where it is under pressure, to the evacuated tank 34. As pressure in the evacuated vessel 34 is built up by reason of the passage of water into the tank 34, the pressure again rises, and certain of the steam theretofore formed may again condense. The degree to which steam and vapor formation occur is dependent upon the temperature and pressure. However, actual practice has shown that blowing the boiler down into the evacuated holding tank 34 operates very satisfactorily, and causes no problems. There is no hammering or other indication that water flow in the blowdown line is slowed by any steam which might form under these conditions.

Referring again to the valve assembly 70a, after a suitable predetermined time period, during which the water in'the tank 34 is allowed to cool, the timer 80 again signals for operation of the motor 75a to rotate the spool to a position of registry shown in FIG. 3d, so as to establish communication between the tank drain line 62 and the outlet line 64. Once again, after sufficient time has elapsed to empty the tank 34, the spool is further rotated to the position of FIG. 3a, wherein all passages are blocked, and where the spool remains until the cycle is to begin again.

As in the operation of the form of apparatus shown in FIG. 1, evacuation of the tank 34 is accelerated by opening valve 36, thus pressurizing the tank 34. In the form of apparatus described in FIGS. 3a-d, the timer 42 controlling operation of the valve 36 is preferably electrically or otherwise associated with the timer 80 so that the tank 34 is opened, and so that the tank drain line 62 is closed prior to closure of the valve 36. In this manner, the tank 34 will again be subject to steam passing through line 32 under pressure so as to repressurize the tank 34.

FIG. 3a also shows a temperature detector 63 operatively associated with the timer 80. This optional feature consists of a temperature detector 63 associated with the tank 34 so as to detect the temperature of the water in the tank, and so as to prevent opening of the tank drain line 62 in the event excessively hot water or steam were somehow present in the tank 34.

No particular type or form of valve, switch, or timer is considered essential to the practice of the invention, and exact pipe or line sizes will depend on the size of the installation. However, in a typical installation, the boiler is of the 400 horsepower rating, having an approximate capacity of 1000 gallons of water and having a normal operating pressure of to lOO p.s.i. or greater. The line 28 is about 1 or 1 /2 inches in size, as are lines 62 and 64. The main steam pressure line 24 is usually 8 to 12 inches in diameter, whereas the steam line 32 is preferably significantly smaller, namely, about /2 to 4 inch pipe. In this connection, it will be noted that the tank 34 may be pressurized to the same effective pressure as that in the headspace 22 regardless of the size of line 32. This pressure abates and is converted to a vacuum when steam in the tank 34 cools and condenses. However, steam at boiler pressure is used to help evacuate the tank 34 by superimposing a pressure on the Water in the tank. A safety factor may inherently be provided by reason of the fact that the small diameter of line 32, in combination with the relatively large volume of the tank 34 and the relatively large size of the drain lines 62, 64 insures that, once the tank 34 is completely empty of sediment-containing water, the steam behind it will have expanded in the tank 34, and in addition to being cooled by expansion and by the optional jacketing of the tank 34, will pass through the drain lines 62, 64 at greatly reduced velocity. Accordingly, the passage of steam through the line 64 for a brief period following tank draining is not damaging or objectionable. If desired, however, this steam may be trapped, as by valve assembly 67, or otherwise, so that it will not pass directly to the atmosphere.

The motor 75a may be a stepping motor, or be operated by a stepping switch for accuracy and repeatability of operation. Such controls are well known in the art.

The constructions described above are very importantly characterized by the fact that the blowdown line from the boiler, which is relatively large and the size of which is selected by conventional considerations, is never opened to the atmosphere by-operation of the various valves and, as pointed out, such valves are designed so that this cannot occureven if the various valves or controls malfunction.

It has been found that the present invention provides a reliable and economical automatic boiler blowdown apparatus and method. The apparatus has the particular advantage of confining the water and steam escaping from the boiler during blowdown to an isolated holding tank, preferably one which is under conditions of partial vacuum during initiation of the cycle. This has been found helpful to add to the turbulence at the.

bottom of the boiler, insuring escape of a desired quantity of sediment. The vacuum also helps eliminate noise and mechanical shock. Boiler blowdown systems made according to the invention either already do, or may easily be-made to, comply with various building codes, including the Boiler and Pressure Vessel Code of the ASME (American Society of Mechanical Engineers) providing for safe operation of boilers. The system of the invention is one which is simple and particularly adapted to be used in applications where the operator has neglected to blowdown the boiler at proper intervals. It is further highly advantageous in that the system may be added to existing boilers without altering other functional or control systems thereof, thereby 'making the boiler operation completely automatic and the attendance of an operator unnecessary for purposes of manual blowdown.

Referring now to certain features which, while not actually necessary to the practice of the invention per se, are desirable from a practical standpoint, or which make operation of the principles of the invention more effective, reference is again made to FIG. 1.

First, it will be noted that a pair of manually operated gate valves 33, 35 are provided, and that these valves 33, 35 are disposed, respectively, in lines 32 and 28. Valve 33 is situated between the main steam line 24 and the valve 36, while valve 35 isdisposed in the blowdown line 28 between the boiler 10. and the valve 66. These manually operated gate valves 33, 35 are provided so that, in the event it is necessary or desirable to service blowdown apparatus 12, the various components thereof can be isolated from the boiler 10. In this -manner, the boiler may continue to operate normally even if the blowdown feature is not used. In some cases, valves of this type are called for bycodes or other standards.

Referring now to another feature shown in FIG. 1, tank 34 is shown to include a water jacket 50. It is anticipated that instead of the jacket 50, a coil of tubes could surround the interior of the tank 34, or might even be disposed inside the tank 34. Regardless of the type of water jacketing or tank cooling means used, control of water flow in the jacketing, coil, or other heat exchanger may be accomplished by providing a valve which permits water flow in proportion to water temperature. Such valves, which may be Penn or similar valves known to those skilled in the art, are commonly used on the water cooled air conditioners or other heat exchangers. Preferably, such a valve would be interconnected with the timer 42 so as to prevent flow in the water jacket while valve 36 is open. This would insure adequate residence time of the jacketing water in the vicinity of the steam in the tank 34 to insure maximum heat transfer.

It is also anticipated that tank 34 can merely be air cooled. Such construction would be most suitable where blowdown of the boiler would be required only once or twice per day or per working shift, for example. In summary, a complete water jacket of the type shown in FIG. 1 is expensive, but may be desired where relatively large heat exchange and/or cooling capacity are needed. A coil arrangement may be used advantageously where the tank 34 is filled less frequently, or where little or no heat exchange capacity is required or desirable. The air cooled arrangement is least expensive and most simple, but provides no heat exchange capacity and requires longer intervals between operation.

In a number of blowdown systems, the blowdown line or pipe is pitched downwardly to avoid accumulation of sediment therein. While this feature may be used with the invention, it is not strictly necessary, because the blowdown water is normally sufficiently turbulent to provide good transfer of the sediment to the tank -34. The curved or tapered bottom wall 46 of the tank 34 insures that sediment will not accumulate in the tank 34. If sediment accumulation were to create a problem, it is anticipated that the tank 34 could be located below line 28 instead of above line 28, with lines 28 and 32 both being directed into the top of the holding tank 34 and with only a drain line 62 or the like coming from the bottom of such tank 34.

In FIG. 1, which is diagrammatic, the tank 34 has been shown with a rounded bottom 46 and a flat top surface 44. It will be understood, as is well known to those skilled in the art, that if the tank 34 is required to hold significant pressure, it would have domed or convex end portions, or otherwise be arranged to retain high pressure with the greatest safety and the least weight and complexity.

FIG. 1 shows schematically that one-way or check valve 49, 51 are provided, respectively, in lines 32 and 28, to prevent backward flow in these lines. Such valves are also commonly required by code or otherwise.

FIG. 1 also shows a pair of gate valves 97, 99 disposed, respectively, in steam lines 24, 26. Placing manually operated valves such as the valves 97, 99 in this position may be desirable and comply with certain codes which may require isolation of the blowdown attachment from the boiler itself, or from some of the lines associated therewith. These valves may be used in conjunction with, or as a replacement for, the valves 33 and 35.

FIG. 3a-3d are merely diagrammatic, and it will be recalled that it is desirable that at least the blowdown valve 66 be opened rapidly to create effective sediment extraction. There may be some cases in which this would not be necessary, however, and in such cases, a valve assembly of the type illustrated at 70a may be sufficient to provide both the line-opening and directioncontrolling functions. It will be understood that a wide variety of valve types may be used in the practice of the invention. By way of further example, the valve assembly 67 may consist of two fast-closing valves or a fastclosing and a slow-closing valve arranged in a manner known to those skilled in the art; it is also contemplated that such valve assembly would not even be required.

Referring now to another feature which may be used with the apparatus of the invention, a counter or sequence timer may be placed in the circuit operating the blowdown valves, so as to indicate to the engineer or operator the number of times during any given time period that the boiler has been blown down. Such arrangement can also, by means known to those skilled in the art, be made to indicate that the cycle has been performed completely and that the apparatus is in fact operating satisfactorily.

It will thus be seen that the present invention'provides a novel blowdown apparatus and method having a number of advantages and characteristics, including those specifically referred to herein and others which are inherent in the invention. Preferred embodiments only having been set forth by way of example, I anticipate that changes and modifications to this apparatus and method will occur to those skilled in the art, and I contemplate that such changes may be made without departing from the spirit of the invention or the scope of the appended claims.

I claimi 1. An apparatus for automatically blowing down a steam boiler, said apparatus comprising, in combination, means for receiving and cooling a charge of high temperature water and sediment blown down from a steam boiler, means for draining said water and sediment from said receiving and cooling means, means providing a blowdown path for water and sediment between a lower portion of saidsteam boiler and the interior of said, receiving and cooling means, normally closed, openable blowdown valve means for controlling the flow of water and sediment in said blowdown path, means for controlling drain flow, and control means for periodically opening said blowdown valve means to permit passage of water and sediment through said blowdown path for short time periods at selected intervals, and for opening said draining means for short time periods at selected intervals, said means for opening said draining means being operable only if said water and sediment have cooled substantially from said high temperature.

2. An apparatus as defined in claim 1 wherein said means for opening said draining means includes a water temperature detector and said means is operable in direct response to a pre-determined temperature detected thereby.

3. An apparatus as defined in claim 1 wherein said control means includes a directional valve constructed and arranged so as to prevent blowdown of said boiler while said drain means is opened, and which prevents opening of said drain means when said boiler blowdown valve means is open.

4. An apparatus as defined in claim 1 wherein said means for receiving and cooling said water and sediment includes a heat exchanger having a medium adapted to be pre-heated by cooling the contents of said receiver, and adapted to conduct said heated medium to a position of heat exchange relation with the contents of the boiler.

5. An apparatus as defined in claim 1 which further includes a steam line adapted to communicate with the interior of a steam boiler blown down by said apparatus, and means for controlling flow of steam between said boiler and said apparatus.

6. An apparatus as defined in claim 5 wherein said siesta valve is adapted to be closed in response to a detected pressure in said receiving and cooling means, and is adapted to be opened in response to a signal from a timer, thereby insuring both full charging of said receiving and cooling means and preventing said means from being charged with steam until after said means has received a charge of water and sediment from said boiler.

7. An apparatus as defined in claim wherein said control means is in the form of a timer for establishing the period during which said steam line is open, and for preventing subsequent opening of said steam line until elapse of a time period sufficient to permit condensation of the steam within said receiving and cooling means.

8. An apparatus as defined in claim 5 wherein said control means is arranged to prevent opening said blowdown valve when said steam valve is open and to prevent opening of said steam valve when said blowdown valve is open, said control means being further adapted to permit opening of said drain valve for a portion of the time during which said steam valve is open.

9. An apparatus for automatically blowing down a steam boiler, said apparatus comprising, in combination, a steam boiler, a holding tank, a steam line communicating with a part of said boiler and with the interior of said holding tank, a normally closed valve in said steam line, a blowdown line extending between a lower portion of the interior of said boiler and the interior of said holding tank, a normally closed valve in said blowdown line, means for draining water and sediment from the interior of said holding tank, a normally closed valve in said drain means, means for opening said steam line valve for a predetermined time sufficient to fill said holding tank with steam, means for opening said blowdown valve for a time sufficient to fill a portion of said holding tank with water and sediment at an elevated temperature, means for opening said drain valve, and control means constructed and arranged so as to open said steam valve when said drain and blowdown lines are closed, to open said blowdown valve when said drain and steam line valves are closed, to cause said drain and steam lines to remain open together, and to cause said drain valve to close before said steam valve closes, said control also providing intervals of time, following opening of said steam valve and opening of said blowdown valve, respectively, during which the contents of said holding tank may cool.

10. An apparatus as defined in claim 9 wherein said means for determining said predetermined time and said sufficient time comprise a timer forming a part of said control means.

11. An apparatus as defined in claim 9 wherein said means for establishing said predetermined time forms a part of said control means and is in the form of a pressure responsive device adapted to close said steam line valve when the steam pressures in said boiler and said holding tank are substantially the same.

12. An apparatus as defined in claim 9 wherein said portion of said control means adapted to cause said drain valve to open is responsive to the temperature of the water and sediment in said holding tank.

13. A method of blowing down a boiler, said method comprising at least partially filling with steam the interior ofa holding tank having a first path of communication between said interior and a boiler steam source, and a second path of communication between said boiler interior and said tank interior, permitting said interior to become evacuated by condensation of said steam therein, blowing down said boiler by rapidly transferring water and sediment from said boiler through said second path to said interior of said holding tank, permitting said water and sediment to cool within said holding tank, expelling said water and sediment from said holding tank by applying positive steam pressure to said tank interior through said first path until all of said water and sediment are expelled, and again pressurizing said holding tank so as to fill said tank at least partially with steam, whereby said blowdown cycle may be repeated.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1 ,605

DATED eptember 30, 1975 vg oms); Charles M. Andersen Hiscmfifiedmatamrmmemsinmeamwe-memfimdpmemandflmtsmdLeflmsPamm amhmwymnmmdwsmwnmmw Column 1, line 10, "in" should be --to- Column 2, line 14, "boiling" should be -holding- Column 2, line 41, "boiling" should be holding Column 5, line 60, "euqal" should be equal Signed and Scaled this Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner uj'larenrs and Trademarks 

1. An apparatus for automatically blowing down a steam boiler, said apparatus comprising, in combination, means for receiving and cooling a charge of high temperature water and sediment blown down from a steam boiler, means for draining said water and sediment from said receiving and cooling means, means providing a blowdown path for water and sediment between a lower portion of said steam boiler and the interior of said receiving and cooling means, normally closed, openable blowdown valve means for controlling the flow of water and sediment in said blowdown path, means for controlling drain flow, and control means for periodically opening said blowdown valve means to permit passage of water and sediment through said blowdown path for short time periods at selected intervals, and for opening said draining means for short time periods at selected intervals, said means for opening said draining means being operable only if said water and sediment have cooled substantially from said high temperature.
 2. An apparatus as defined in claim 1 wherein said means for opening said draining means includes a water temperature detector and said means is operable in direct response to a pre-determined temperature detected thereby.
 3. An apparatus as defined in claim 1 wherein said control means includes a directional valve constructed and arranged so as to prevent blowdown of said boiler while said drain means is opened, and which prevents opening of said drain means when said boiler blowdown valve means is open.
 4. An apparatus as defined in claim 1 wherein said means for receiving and cooling said water and sediment includes a heat exchanger having a medium adapted to be pre-heated by cooling the contents of said receiver, and adapted to conduct said heated medium to a position of heat exchange relation with the contents of the boiler.
 5. An apparatus as defined in claim 1 which further includes a steam line adapted to communicAte with the interior of a steam boiler blown down by said apparatus, and means for controlling flow of steam between said boiler and said apparatus.
 6. An apparatus as defined in claim 5 wherein said steam valve is adapted to be closed in response to a detected pressure in said receiving and cooling means, and is adapted to be opened in response to a signal from a timer, thereby insuring both full charging of said receiving and cooling means and preventing said means from being charged with steam until after said means has received a charge of water and sediment from said boiler.
 7. An apparatus as defined in claim 5 wherein said control means is in the form of a timer for establishing the period during which said steam line is open, and for preventing subsequent opening of said steam line until elapse of a time period sufficient to permit condensation of the steam within said receiving and cooling means.
 8. An apparatus as defined in claim 5 wherein said control means is arranged to prevent opening said blowdown valve when said steam valve is open and to prevent opening of said steam valve when said blowdown valve is open, said control means being further adapted to permit opening of said drain valve for a portion of the time during which said steam valve is open.
 9. An apparatus for automatically blowing down a steam boiler, said apparatus comprising, in combination, a steam boiler, a holding tank, a steam line communicating with a part of said boiler and with the interior of said holding tank, a normally closed valve in said steam line, a blowdown line extending between a lower portion of the interior of said boiler and the interior of said holding tank, a normally closed valve in said blowdown line, means for draining water and sediment from the interior of said holding tank, a normally closed valve in said drain means, means for opening said steam line valve for a predetermined time sufficient to fill said holding tank with steam, means for opening said blowdown valve for a time sufficient to fill a portion of said holding tank with water and sediment at an elevated temperature, means for opening said drain valve, and control means constructed and arranged so as to open said steam valve when said drain and blowdown lines are closed, to open said blowdown valve when said drain and steam line valves are closed, to cause said drain and steam lines to remain open together, and to cause said drain valve to close before said steam valve closes, said control also providing intervals of time, following opening of said steam valve and opening of said blowdown valve, respectively, during which the contents of said holding tank may cool.
 10. An apparatus as defined in claim 9 wherein said means for determining said predetermined time and said sufficient time comprise a timer forming a part of said control means.
 11. An apparatus as defined in claim 9 wherein said means for establishing said predetermined time forms a part of said control means and is in the form of a pressure responsive device adapted to close said steam line valve when the steam pressures in said boiler and said holding tank are substantially the same.
 12. An apparatus as defined in claim 9 wherein said portion of said control means adapted to cause said drain valve to open is responsive to the temperature of the water and sediment in said holding tank.
 13. A method of blowing down a boiler, said method comprising at least partially filling with steam the interior of a holding tank having a first path of communication between said interior and a boiler steam source, and a second path of communication between said boiler interior and said tank interior, permitting said interior to become evacuated by condensation of said steam therein, blowing down said boiler by rapidly transferring water and sediment from said boiler through said second path to said interior of said holding tank, permitting said water and sediment to cool within said holding tank, expelling said water and sediment from said holDing tank by applying positive steam pressure to said tank interior through said first path until all of said water and sediment are expelled, and again pressurizing said holding tank so as to fill said tank at least partially with steam, whereby said blowdown cycle may be repeated. 